1. Field of the Invention
The present invention is related to computer systems for generating, managing and validating reference handles of consumers requiring access to resources.
2. Related Art
The following co-pending applications are assigned to the same Assignee as the present invention: (1) U.S. patent application Ser. No. 09/103,334 filed Jun. 23, 1998, entitled "Generation And Validation Of Reference Handles" by John R. Douceur et al., Docket No. MCS-017A-98; (2) U.S. patent application Ser. No. 09/103,297 filed Jun. 23, 1998, entitled "Generation and Validation Of Reference Handles in A Multithreading Environment" by John R. Douceur et al., Docket No. MCS-017B-98; (3) U.S. patent application Ser. No. 09/103,333 filed Jun. 23, 1998, entitled "System and Method For Reducing Location Conflicts In a Database" by John R. Douceur et al., Docket No. MCS-017D-98; (4) U.S. patent application Ser. No. 09/103,089 filed Jun. 23, 1998, entitled "System and Method For Recycling Numerical Values In A Computer System" by John R. Douceur et al., Docket MCS-017E-98.
It is not uncommon for software modules operating on computer systems to require access to shared resources. For example, a given computer program may require access to files maintained by a file system, or it may require access to network connections maintained by a network driver. Network drivers may require access to information structures maintained by a network packet classifier. This is a complex arrangement that includes numerous software modules, such as software drivers requiring access to many shared resources and an access supervisor that either maintains the resources or at least intercedes in access by the software modules to the resource.
Such intercession exists for several reasons, one especially important reason being when a software module deletes a resource. If a first software module were to delete a first resource, while other software modules maintain direct pointers to the first resource, the pointers of the other software modules would be unaware of the deletion of the resource and would no longer point to a valid resource. Attempts have been made to solve this problem by notifying software modules when a resource deletion occurs. However, this requires detailed accounting and tracking of software modules and their respective pointers to the resources. As a result, this process is extremely expensive and very complex.
Another attempt to solve this problem involves having an access supervisor intercede when a software module requires access to a particular resource. Interceding ensures that the particular resource still exists before the software module is granted access to the particular resource. Typically, this is accomplished by having the access supervisor issue to each software module a handle to a particular resource, rather than allowing each software module a direct pointer to that particular resource. The software module does not use the handle to access the resource directly. Instead, the software module presents the handle to the access supervisor, which can dereference the handle to obtain a pointer to the resource for that software module. Although this approach allows the access supervisor to have control over the management of the shared resources, prior methods that follow this approach provide only rudimentary control, and thus have several limitations.
First, prior methods are inefficient, expensive and limited in their use because they lack constant-time operations, which is a problem when the number of simultaneously active handles is large. Also, the handle databases of prior methods have limited flexibility because they are not capable of growing and shrinking arbitrarily in an efficient manner. In addition, prior methods lack fast and efficient dereferencing and are ineffective in a multi-threaded environment. Further, prior methods lack efficient processes for recycling handles to increase handle space and to optimize the handle database. Therefore, what is needed is a computer-implemented system for generating and validating reference handles effectively and efficiently that overcomes these limitations.
Whatever the merits of the prior systems and methods, they do not achieve the benefits of the present invention.